1. Field of the Invention
This invention relates to copper based metal alloys and more particularly to a homogeneous, ductile brazing material useful for brazing metal articles such as those composed of copper and copper alloys.
2. Description of the Prior Art
Brazing is a process of joining metal parts, often of dissimilar composition, to each other. Typically, a filler metal that has a melting point lower than that of the metal parts to be joined together is interposed between the metal parts to form an assembly. The assembly is then heated to a temperature sufficient to melt the filler metal. Upon cooling, a strong, leak-tight joint is formed. Filler metals used are commonly is powder, wire or foil form depending on the type of application. Foil form provides the advantage of preplacing the filler metal in the joint area, thus permitting brazing of complex shapes with minimum rejection.
The brazing alloys suitable for use with copper and copper alloys, designated AWS BAg are well known compositions. These alloys contain substantial amounts of the precious metal silver (19 to 86 weight percent) and hence are expensive. Most of the AWS BAg compositions are fabricated to a foil form through a lengthy sequence of rolling and annealing, thereby incurring substantial processing cost.
Ductile glassy metal alloys have been disclosed in U.S. Pat. No. 3,856,513, issued Dec. 24, 1974 to H. S. Chen et al. These alloys include compositions having the formula T.sub.i X.sub.j, where T is at least one transition metal and X is an element selected from the group consisting of phosphorus, boron, carbon, aluminum, silicon, tin, germanium, indium, beryllium and antimony, "i" ranges from about 70 to about 87 atom percent and "j" ranges from about 13 to 30 atom percent. Such materials are conveniently prepared in powder, wire or foil form by rapid quenching from the melt using processing techniques that are now well-known in the art. However, no liquid-quenched glassy metal alloys of the family T.sub.i X.sub.j described above, containing copper as the principal transition metal have been reported. Chen et al. report only one copper containing composition (e.g. Pd.sub.77.5 Cu.sub.6 Si.sub.16.5) in U.S. Pat. No. 3,856,513. H. Suto and H. Ishikawa, Trans. Japan Inst. of Metals, V. 17, 1976, p. 596, report fabrication of glassy Cu-Si by vapor deposition.
There remains a need in the art for a homogeneous brazing material for joining copper and copper alloys that is free of precious metals and can be produced in foil, powder or wire form.